Although not ideal, missing birth control pills is a fairly common occurrence. Due to this, manufacturers of birth control pills put specific directions on what to do if you miss pills in the package insert provided with the medication.

From your question, we are assuming that you mean your menstruation period (shedding of the uterine walls), instead of your ovulation period (when the egg is released). Ovulation typically occurs half-way through your menstrual cycle, at about day 12-14. Menstruation is actually the mark of the beginning of a cycle, although most people perceive this as the end of a cycle since it coincides with the last week of birth control pills. So again, we are assuming your question is regarding your last week of pills (right before menses).

According to the package insert for Yaz, they provide the following instructions:

  • If you MISS 2 light pink "active" pills in a row in WEEK 3 or Week 4 of your pack:
  •  If you are a Day 1 Starter: THROW OUT the rest of the pill pack and start a new pack that same day. 
  • If you are a Sunday Starter: Keep taking one pill every day until Sunday. On Sunday, THROW OUT the rest of the pack and start a new pack of pills that same day. You COULD BECOME PREGNANT if you have sex in the 7 days after you restart your pills. You MUST use another birth control method (such as condoms or spermicides) as a back-up for those 7 days. You may not have your period this month but this is expected. However, if you miss your period two months in a row, call your healthcare provider because you might be pregnant. 

The risk of pregnancy in your situation is greater if you are a "Sunday Starter" and the package insert mentions that specifically. The risk of pregnancy is much less if you are a "Day One" starter.

There is always a risk of pregnancy when unprotected sex occurs, even if you are on birth control pills. Missing doses or not taking them consistently certainly does increase that risk, but it does vary based on how many pills you missed and how you started the pack. If you are concerned about pregnancy, I recommend talking to your health care provider and they can give you some options including information on the Plan B medication ('day after pill') or pregnancy testing advice.​